Despite the occasional confusion about wills, they can be changed.
“Mirror image wills” often turn out to be a common source of litigation, according to the National Law Review in "Contracts to Make Wills or Trusts."
The “mirror image will” is usually where spouses agree that the first to pass away, will leave everything to the surviving spouse, with the second to pass away agreeing to leave the estate to the agreed upon heirs.
The problem starts when the surviving spouse has a change of plans and changes his or her will to divide things differently, or to give the estate to different heirs.
The heirs of the original mirror image wills routinely argue in court, that the spouses entered into a contract to make the original wills. Unfortunately, that is simply not the case in almost all circumstances.
To be valid, a contract requires that a person receive some sort of compensation, called consideration, for whatever promise it is that they are contracted to perform.
In the case of mirror image wills, spouses rarely receive any form of consideration for promising not to change the will later.
It is important to understand this point, because the issue frequently comes up in estate litigation. It costs estates a lot of money when the issue is raised.
An estate planning attorney can guide you in creating a will and estate plan that meets your unique circumstances.
Reference: National Law Review (April 10, 2017) "Contracts to Make Wills or Trusts."